Add EventPipe interop instrumentation for wrapper lifecycle and GC-bridge reachability by Copilot · Pull Request #12258 · dotnet/android

Copilot · 2026-07-28T21:02:56Z

This adds first-class EventPipe visibility into the .NET↔Java interop layer so wrapper lifecycle and cross-runtime reachability transitions can be observed in production traces. The instrumentation covers wrapper creation/release on both sides and GC-bridge reachability state transitions with correlation data.

New interop EventSource provider
- Added a single provider: Java.Interop
- Added stable event IDs/keywords for:
  - DotNetWrapperCreated
  - JavaWrapperCreated
  - DotNetWrapperReleasedJavaReference
  - JavaWrapperReleasedDotNetReference
  - DotNetObjectOnlyReachableFromJava
  - JavaObjectOnlyReachableFromDotNet
- Standardized payload fields: managed type, Java type, JNI identity hash, managed object hash, runtime mode; reachability events also include component/context correlation fields.
Wrapper creation instrumentation
- Emitted .NET wrapper for Java object events from:
  - ReflectionJniValueManager.CreatePeer
  - TrimmableTypeMapValueManager.CreatePeer
  - AndroidRuntime.AndroidValueManager.CreatePeer
- Emitted Java wrapper for .NET object events from:
  - ManagedPeer.Construct
  - ConstructPeerCore paths where Java peer references are established
Wrapper release instrumentation
- Emitted .NET wrapper releases Java reference from disposal/finalization paths:
  - JniValueManager.DisposePeer
  - JavaMarshalRegisteredPeers.FinalizePeer
- Emitted Java wrapper releases .NET reference from registered-peer removal:
  - JavaMarshalRegisteredPeers.RemovePeer
GC-bridge reachability instrumentation
- Emitted reachability-transition events from JavaMarshalRegisteredPeers bridge processing:
  - .NET object only reachable from Java
  - Java object only reachable from .NET
- Included bridge round correlation data (componentIndex, contextIndex, contextPointer) for trace-side reconstruction.
Low-overhead event gating
- Guarded all instrumentation paths with InteropEventSource.IsEnabled() before payload-heavy work (e.g., Java type resolution) to avoid unnecessary overhead when no listener is attached.
API, tests, and docs
- Added public API entries for InteropEventSource.
- Added Java.Interop unit tests validating event emission and payload shape.
- Added runtime-facing tests in Mono.Android for lifecycle event behavior.
- Added event catalog and dotnet-trace usage documentation.

if (InteropEventSource.IsEnabled ()) {
	InteropEventSource.DotNetWrapperCreated (
		peer.GetType ().FullName,
		javaType,
		peer.JniIdentityHashCode,
		RuntimeHelpers.GetHashCode (peer),
		GetRuntimeMode ());
}

Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot

Pull request overview

This PR introduces EventPipe instrumentation across the .NET↔Java interop layer to make wrapper lifecycle and GC-bridge reachability transitions observable in production traces via a new Java.Interop EventSource provider.

Changes:

Added a new Java.Interop EventSource (InteropEventSource) with stable event IDs/keywords and a documented payload schema.
Instrumented wrapper creation/release in Java.Interop value managers + Mono.Android runtime, and added GC-bridge reachability transition events with correlation fields.
Added unit tests (Java.Interop) and runtime-facing tests (Mono.Android) plus documentation for capturing with dotnet-trace.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/InteropEventSourceRuntimeTests.cs	Runtime tests validating lifecycle events are emitted on-device/in-runtime.
src/Mono.Android/Microsoft.Android.Runtime/TrimmableTypeMapValueManager.cs	Emits wrapper creation events for trimmable typemap value manager paths.
src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalRegisteredPeers.cs	Emits wrapper release + GC-bridge reachability events during bridge processing.
src/Mono.Android/Android.Runtime/AndroidRuntime.cs	Emits wrapper creation events for `AndroidValueManager.CreatePeer`.
external/Java.Interop/tests/Java.Interop-Tests/Java.Interop/InteropEventSourceTests.cs	Unit tests validating EventSource emission and payload shape.
external/Java.Interop/src/Java.Interop/PublicAPI.Unshipped.txt	Declares new public API surface for `InteropEventSource`.
external/Java.Interop/src/Java.Interop/Java.Interop/ManagedPeer.cs	Emits `JavaWrapperCreated` during managed-peer construction from Java.
external/Java.Interop/src/Java.Interop/Java.Interop/JniRuntime.ReflectionJniValueManager.cs	Emits wrapper creation events in reflection-based value manager.
external/Java.Interop/src/Java.Interop/Java.Interop/JniRuntime.JniValueManager.cs	Emits wrapper release events during peer disposal.
external/Java.Interop/src/Java.Interop/Java.Interop/InteropEventSource.cs	New provider implementation + event definitions/keywords.
external/Java.Interop/Documentation/EventPipeInteropEvents.md	Event catalog, payload schema, and `dotnet-trace` collection instructions.

jonathanpeppers · 2026-07-29T16:08:46Z


 		peer.SetPeerReference (newRef);
 		peer.SetJniIdentityHashCode (JniEnvironment.References.GetIdentityHashCode (newRef));
+		if (!peer.JniManagedPeerState.HasFlag (JniManagedPeerStates.Activatable) && InteropEventSource.IsEnabled ()) {


Can InteropEventSource.IsEnabled () be backed by a trimmer feature switch that is off by default? We have a RuntimeFeature.cs where we enable these.

+				if (!peer.JniManagedPeerState.HasFlag (JniManagedPeerStates.Activatable) && InteropEventSource.IsEnabled ()) {
+					EmitJavaWrapperCreatedEvent (peer, newRef);
+				}


+					if (InteropEventSource.IsEnabled ()) {
+						EmitJavaWrapperReleasedDotNetReference (value);
+					}
 					peers.RemoveAt (i);
 					peer.Dispose ();
 				}


+		public static bool IsEnabled ()
+		{
+			return source.IsEnabled ();
+		}


+			string GetRuntimeMode ()
+			{
+				return Runtime.GetType ().FullName ?? "Unknown";
+			}


+				if (InteropEventSource.IsEnabled ()) {
+					var javaType = JniEnvironment.Types.GetJniTypeNameFromInstance (h);
+					InteropEventSource.DotNetWrapperReleasedJavaReference (
+						value.GetType ().FullName,
+						javaType,
+						value.JniIdentityHashCode,
+						RuntimeHelpers.GetHashCode (value),
+						Runtime.GetType ().FullName);
+				}


+				if (InteropEventSource.IsEnabled ()) {
+					var managedObjectHashCode = self != null ? RuntimeHelpers.GetHashCode (self) : 0;
+					InteropEventSource.JavaWrapperCreated (
+						type.FullName,
+						typeSig.SimpleReference,
+						runtime.ValueManager.GetJniIdentityHashCode (r_self),
+						managedObjectHashCode,
+						runtime.GetType ().FullName);
+				}


jonathanpeppers · 2026-07-29T16:06:42Z

+
+namespace Java.Interop
+{
+	public static class InteropEventSource


Does this need to be public? I'd rather users opt into this logging with settings (either MSBuild property/trimmer switch or Android system property)

And then we'd need no public APIs at all?

jonathanpeppers · 2026-07-29T16:07:57Z

+		public static void DotNetWrapperCreated (
+				string? managedType,
+				string? javaType,
+				int jniIdentityHashCode,
+				int managedObjectHashCode,
+				string? runtimeMode)
+		{


The naming choices here seem odd, e.g. DotNetWrapper. Can we use pre-existing terminology? You might look in external/java.interop/docs/ for examples.

jonathanpeppers · 2026-07-29T16:08:46Z


 		peer.SetPeerReference (newRef);
 		peer.SetJniIdentityHashCode (JniEnvironment.References.GetIdentityHashCode (newRef));
+		if (!peer.JniManagedPeerState.HasFlag (JniManagedPeerStates.Activatable) && InteropEventSource.IsEnabled ()) {


Can InteropEventSource.IsEnabled () be backed by a trimmer feature switch that is off by default? We have a RuntimeFeature.cs where we enable these.

jonathanpeppers · 2026-07-29T16:09:35Z

+The .NET ↔ Java interop layer emits EventPipe events through a single provider:
+
+- **Provider name:** `Java.Interop`
+
+## Event catalog
+
+| Event ID | Event name | Meaning |
+|---|---|---|
+| 1 | `DotNetWrapperCreated` | A managed wrapper for a Java object was created. |
+| 2 | `JavaWrapperCreated` | A Java wrapper for a managed object was created. |
+| 3 | `DotNetWrapperReleasedJavaReference` | A managed wrapper released its Java reference. |
+| 4 | `JavaWrapperReleasedDotNetReference` | A Java wrapper released its managed reference. |
+| 5 | `DotNetObjectOnlyReachableFromJava` | A managed object is only reachable from Java during bridge processing. |
+| 6 | `JavaObjectOnlyReachableFromDotNet` | A Java object is only reachable from .NET during bridge processing. |


There is some existing code in here for writing gref/lref logs. It is old and text-based. Does this replace or supplement this?

Copilot AI and others added 2 commits July 28, 2026 00:17

Add interop EventSource and instrumentation hooks

447c870

Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Add interop EventPipe tests and fixups

e9eee27

Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot AI assigned Copilot and jkoritzinsky Jul 28, 2026

Copilot created this pull request from a session on behalf of jkoritzinsky July 28, 2026 21:02 View session

jkoritzinsky marked this pull request as ready for review July 28, 2026 21:03

jkoritzinsky requested review from jonathanpeppers and simonrozsival as code owners July 28, 2026 21:03

Copilot AI review requested due to automatic review settings July 28, 2026 21:03

Copilot started reviewing on behalf of jkoritzinsky July 28, 2026 21:03 View session

Copilot AI reviewed Jul 28, 2026

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jonathanpeppers reviewed Jul 29, 2026

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Add EventPipe interop instrumentation for wrapper lifecycle and GC-bridge reachability - #12258

Add EventPipe interop instrumentation for wrapper lifecycle and GC-bridge reachability#12258
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